1. Field of the Invention
The present invention relates to a reflect array antenna and, more particularly, to a stacked microstrip reflect array antenna.
2. Description of the Related Art
In the field of high frequency communications, in order to provide better communication bandwidth, a reflect array antenna is employed to receive and send signals. As shown in FIG. 1, U.S. Pat. No. 6,195,047/B1, entitled “Integrated microelectromechanical phase shifting reflect array antenna”, discloses a microstrip phase shifting reflect array antenna 10 which includes a substantially flat circular disk 12 upon which a plurality of array elements 14 are disposed in a regular and repeating pattern. As shown in FIG. 1, array elements 14 are arranged in rows and columns on the disk 12. A feed horn 16 is located above the disk 12, either offset (as shown) or centered, over the plurality of array elements 14. Array elements 14 are placed on an upper surface of a thicker flat panel 18. Due to the special design of the array elements 14, a signal can be reflected to the feed horn 16; therefore, a relative position between the horn 16 and the disk 12 is fixed. When the reflect array antenna 10 receives a remote communication signal, the plurality of array elements 14 on the disk 12 reflect and focus the communication signal to the horn 16, so the horn 16 receives the communication signal with a better signal gain and a wider bandwidth. Furthermore, the reflect array antenna 10 can use the horn 16 to transmit another communication signal via the disk 12.
In order to obtain better signal gain and a wider bandwidth, the patterns of the array elements 14 are not identical. As shown in FIG. 2, all of the array element 141, the array element 142 and the array element 144 have a delay line with different lengths, while an array element 143 has no delay line. The delay lines are used for adjusting a phase of the communication signal to determine a main beam direction that the array element is to reflect, so that the communication signal reflected by the array element can be focused onto the horn 16. A user can rotate the array elements 14 so they have different angles. Alternatively, as shown in FIG. 3, an array element 145 has different delay lines (including a linear delay line 1451 and a curved delay line 1452) and is rotated for better signal gain and a wider bandwidth.
However, the prior art shifting reflect array antenna 10 has some drawbacks, such as a relatively limited signal gain, a narrow bandwidth and proper delay line arrangement to avoid cross-polarization.
Therefore, it is desirable to provide a stacked microstrip reflect array antenna to mitigate and/or obviate the aforementioned problems.